Structure/Property Relationship for Ethylenediamine Derivatives as Aids in Sunless Tanning

This report covers an effort to identify adjuvants to the sunless tanning action of dihydroxyacetone. The readily available derivatives of ethylenediamine were systematically studied for their coloration behavior with DHA on synthetic skin, resulting in the following structure/activity relationship: 1) Linear derivatives with each of the amines either primary or secondary with respect to methyl substitution gave very rapid coloration, as did cyclic derivatives in which the ethylenediamine backbone was fully embedded in the ring and both amines are primary or partially embedded with the external amine primary; 2) Stretched derivatives in which the ethylene moiety is changed to propylene or longer gave progressively less coloration; 3) Derivatives of ethylenediamine in which either or both of the amines were tertiary with respect to alkyl substitution yielded no adjuvant action. The observed behavior can be rationalized in terms of the Maillard reaction being a complex network of reactions in which the chemical structure of the adjuvant controls, at least in part, the reaction pathway. For ethylenediamines, it appears that a highly reactive pathway exists which involves a six-membered ring with the amine groups at the 1,4 positions. Thus stretched diamines and tertiary amines are restricted from taking this route.